Ability to have additional images for the workshop cards

As a partner I would like to be able to apply my company's logo to the workshop card instead of the stock image.

Start by locating the workshop card implementation and the code that selects its stock image; no file or test is named in the issue. The work is done when a partner can apply a company logo to the card instead of the stock image, with the existing card presentation preserved.

Written by the indexing model from the issue text.